The World Is Bigger Than You Think
The Earth currently has a population of 6.85 billion. With a total land mass of 148.65 million square kilometers*, this implies a population density of about 46 per square kilometer. True, it is arguably misleading to include Antarctica'a land mass as it is basically uninhabitable due to the intolerably cold conditions, but even then we still have 133,93 million square kilometers of land, implying a population density of about 51 per square kilometer.
By contrast, In Singapore we have 5 million -very prosperous- people on a mere 710 square kilometers, implying a population density of over 7,000 per square kilometer.
And yet despite this unusually high population density, Singapore still find room for several military bases (with the Army, the Air Force and Navy each having several bases) as well as a national park.
If the world -excluding Antarctica-, had only a tenth of the population density of Singapore, thus allowing quite a lot of military bases and parks and agricultural fields, then it would still be room for 93 billion people, which is to say nearly 14 times as many as today.
Thus, there is no risk at all of the world becoming over-population in the sense of becoming over-crowded. And "over-population" in the sense of not having enough resources is only a risk if socialist and other irrationalist ideas prevent the expansion of output.
*1 square kilometer is roughly equal to 0.39 square miles.